Super Sticky Power

Scientists have long been fascinated by the gravity-defying skills of geckos. The lizardlike creatures can walk up walls and across ceilings.

In recent years, researchers have discovered that tiny hairs on the pads of their feet give geckos their power to stick. Engineers have mimicked those structures to create sticky materials. (See “How a Gecko Defies Gravity”).

Gecko-inspired sticky substances, however, don’t stick as well as real geckos do. In particular, after being repeatedly stuck and unstuck, the substances become less adhesive.

To improve their material, scientists from Northwestern University in Evanston, Ill., enlisted the help of a second sticky creature: the mussel. Mussels look sort of like clams, and they live in lakes, rivers, and oceans. The shelled animals are really good at sticking to rocks, boats, and other objects. They can even stay put when powerful waves batter them.

What’s the mussel’s sticky secret? Through their feet, mussels secrete a protein, and part of that protein bonds them to underwater surfaces. Scientists call the substance 3,4-dihydroxy-L-phenylalanine—DOPA, for short.

To make their new material, scientists started with a base of tiny, geckolike hairs. Each hair was 400 nanometers (nm) wide and 600 nm tall. A nanometer is one-billionth of a meter. (To get a sense of how little that is, a human hair is about 8,000 nanometers wide.)

The scientists coated these hairs with a molecule that contained DOPA. The result was a substance that could stick to objects much like adhesive tape does. The new material can stick and restick more than 1,000 times without losing strength. And it has a second big advantage: It works almost as well when it’s wet as it does when it’s dry.

The product is “kind of like a Post-it,” says team leader Phillip Messersmith.

The material the researchers produced was just half a square centimeter (0.08 square inch) in size. If the scientists can make larger pieces of the sticky stuff, they envision a number of applications in medicine. Imagine, for example, bandages that stay on your knees, even when you’re swimming or plunging down a waterslide. Doctors could use the material to close wounds in patients who’d undergone surgery.

What did the scientists name a material that combines the power of geckos with the power of mussels? “Geckel,” of course.—Emily Sohn

Going Deeper:

Webb, Sarah. 2007. Gecko adhesive gets added mussel. Science News 172(Aug. 4):78. Available at http://www.sciencenews.org/articles/20070804/note16.asp .

McDonagh, Sorcha. 2004. Gooey secrets of mussel power. Science News for Kids (Jan. 21). Available at http://www.sciencenewsforkids.org/articles/20040121/Note2.asp .

Sohn, Emily. 2003. How a gecko defies gravity. Science News for Kids (Nov. 19). Available at http://www.sciencenewsforkids.org/articles/20031119/Feature1.asp .